1. Field of the Invention
The present invention relates to a sealing device for sealing at least one underpressure or overpressure zone adjoining a moving surface which is moving in a direction of travel in a paper, tissue or cardboard machine. The sealing device includes at least one sealing element which is located opposite the moving surface and has at least one feeding channel for lubricant.
2. Description of the Related Art
Sealing devices of this type are used in practice in the forming section as well as in the press section and/or the drying section of a respective paper machine application where among other possibilities they can be installed in suction rolls or blow rolls. Suction boxes are generally equipped with stationary internal suction boxes which form, for example, adjustable zones with at least one pressure level, whereby sealing of the pressure or vacuum zones occurs in a direction of travel of the paper machine fabric by means of sealing strips which generally extend across the entire roll length. The roll shell is perforated so that, for example, water from a fabric can be discharged through the holes in the shell into the suction zone and can subsequently be transported out of the roll.
To seal the vacuum on suction equipped roll types in the direction of travel of the paper machine fabric or respectively in the direction of movement of the moving surface, strip-like sealing elements (therefore also referred to as sealing strips) which have a continuous sealing surface are used which are in contact with the inside surface of the roll shell, in other words with the aforementioned moving surface. The sealing element in this case is subjected to relatively high wear and tear resulting from abrasion and temperature development, so that the sealing element in practical use must be continuously readjusted. After removal of the maximum wear layer the roll must be opened and the sealing element must be replaced.
To cool a sealing element, but also to lubricate it, it is often sprayed with a cool lubricant over its entire length, for example with spray nozzles. However, suction rolls comprise for example at least two sealing elements, whereby, viewed in direction of rotation of the shell only the first sealing strip benefits, because the lubricant is usually already completely doctored off in this location so that it is not carried to the second sealing strip. The spray nozzles are moreover susceptible to contamination.
To cool the sealing element it was suggested in DE 103 25 686 A1 to equip a sealing element with closed lines through which a cooling agent flows.
To reduce wear and tear it is known from WO 2007003698 A1 to incorporate a radial feeding channel into the sealing element to be able to supply a lubricant into the region between the interior surface of the shell and the sealing element. In a trial a retrofit of this design has shown that it leads to uneven wear of the sealing element in the cross machine (CD)-direction and is therefore not expedient.
What is needed in the art is to clearly and uniformly reduce wear of a sealing element over its entire length.